I have 3 classes in my example: Class A, the main activity. Class A calls a startActivityForResult:
Intent intent = new Intent(this, ClassB.class);
startAct
For start Activity 2 from Activity 1 and get result, you could use startActivityForResult and implement onActivityResult in Activity 1 and use setResult in Activity2.
Intent intent = new Intent(this, Activity2.class);
intent.putExtra(NUMERO1, numero1);
intent.putExtra(NUMERO2, numero2);
//startActivity(intent);
startActivityForResult(intent, MI_REQUEST_CODE);